Convergence unit for picture receiving tubes



May 7, 1957 L. G. LANDES ET AL 2,791,709

CONVERGENCE UNIT FOR PICTURE RECEIVING TUBES Filed July 29, 1955 IN VEN TORJ.

10w: 6. Ana 04's. BY P6727? J Dar/rm fl/l ilnited States Patent 2,7 91 ,7 09 CONVERGENCE UNIT gglsPlCTURE RECEIVING Lewis G. Landes, Paris, Ill., and Peter J. Davitto, Terre Haute, Ind., assignors to Meco, Inc., Paris, lit, a corporation Application July 29, 1955, Serial No. 525,273

9 Claims. (Cl. 313-77) This invention relates generally to units for controlling the convergence of a plurality of cathode ray beams in picture receiving tubes and more particularly it relates to an electromagnetic unit adapted to be clamped to the neck of a cathode ray tube for controlling the convergence point of a plurality of cathode ray beams.

in color television receivers there is provided a picture receiving tube having a number of electron guns for generating electron beams, for controlling reproduction of each color in the received picture. Because of the fact that it is diflicult to position electron guns with absolute accuracy within the picture receiving tube it is found that the beams emitted by the guns do not intersect at a common point. Therefore, it is necessary to provide magnetic fields in the paths of the electron beams for the purpose of causing the beams to intersect at a common point.

it is also necessary to provide further control of the point of intersection of a plurality of electron beams during and in accordance with scanning deflection of the beams. The picture reproduction screen is curved whereby all point thereon are not equidistant from the electron guns. Accordingly, electromagnets are energized from the deflection circuits of the television receiver to create magnetic fields varying in accordance with deflection of the beams to cause the beams to converge as nearly as possible in the plane of the curved surface of the picture reproducing screen.

Prior beam convergence units of the type described have been mounted on the neck of the picture receiving tube in various ways, but such mountings have been awkward to assemble on the neck of the tube, and the electromagnets have been diflicult to adjust for the purpose of obtaining accurate convergence of the electron beams. For example, one conventional type of convergence unit utilizes permanent magnets in the form of rods and adjustably mounted for rotation between a pair of pole pieces.

During adjustment of such rods there is sufficient wear on the rod surfaces and on the pole piece surfaces to cause a loose fit, whereby the rods do not hold proper adjustment and accordingly the beams do not converge to a single point of intersection.

The principal object of this invention is to provide a convergence unit for picture receiving tubes wherein a hinged frame structure is adapted to support a number of electromagnetic units on the neck of the picture receiving tube, the frame structure being adapted to be opened for mounting over the tube neck and to be closed and latched with the pole pieces of the electromagnet in firm engagement with the tube neck.

Another object of this invention is to provide a convergence unit for picture receiving tubes having electromagnets and adjustable permanent magnets mounted in such relation that permanent adjustment is obtainable.

In accordance with this invention there is provided a convergence unit for multibeam receiving tubes which comprises a frame having three sections, two of which ice are hinged to the other, and electromagnets spring supported on each frame section, each electromagnet having an adjustable permanent magnet rotatably mounted on and spring pressed into engagement with the electromagnet for adjustment with respect thereto.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

Fig. 1 is a side elevational view of the convergence unit provided in accordance with this invention.

Fig. 2 is a cross section taken on the line 2--2 of Fig. l, and illustrating the structure of a single electromagnet.

The convergence unit provided in accordance with this invention comprises a frame structure having a section it? to which are hinged the similar sections 11 and 12. Section it), for example, includes on one side of its base portion an car 14 having formed therein an aperture 15. On the other side of the base portion of section 10 there is provided a flanged extension is in which is mounted a pin 17. The section 11 is connected to section 10 by means of a flanged portion 18 having a pin 19 adapted to fit within aperture 15. Section 11 also includes a stop tab 20 which overlaps the ear 14, locking car 14 over pin 19 for rotation thereon, and limiting the rotation of section 11 with respect to section 10.

Similarly, section 12 includes an ear member 21 having an aperture 22 for receiving the pin 17 and section 10 includes an overlaping stop tab 23 which holds the ear member 21 in engagement with pin 17 for rotation thereon and limits the rotation of section 12 with respect to section 10. Thus, sections 11 and 12 may be rotated on pins 15 and 17, respectively, so that the unit may be opened and closed about the neck 24 of a picture receiving tube.

Section 11 is also provided with an ear portion 25 on the leg opposite to that hearing the flanged portion 18. The ear 25 is slotted at 26 to receive a pin 27 supported in a flanged portion 29 formed on the leg of section 12 opposite to that bearing ear 21. The car 25 includes an extended finger 39 adapted to engage with a flange 31 formed on portion 29, thereby to positively engage the wall of slot 26 with pin 27. Dotted lines 33, 34 and 35 illustrate the positions of sections 10, 11 and 12 from which the ear 25 is moved to engage the walls of slot 26 with pin 27. The flanged portion 29 also includes an overlapping tab 36 extending over car 25 and serving to hold car 25 downwardly over pin 27 and to stop excessive rotation of section 11 with respect to section 12.

The frame sections 10, 11 and 12 serve to support the electromagnets 38, 39 and 40, respectively. Each of the electromagnets is identical in structure and comprises a coil 42 mounted on and secured to, in any suitable fashion, the cross member 43 of section 10, for example. A pair of relatively soft iron pole pieces 45 and 46 may be slideably mounted within the coil 42 for movement toward and away from the tube neck 24. The pole pieces 45 and 46 are L-shaped and abut one another as at 47, thereby to provide a fiux path.

The coils 42 provide dynamic correction of beam convergence. They are electrically connected to beam dcflection circuits of a color television receiver, for example, and operate to vary, with deflection, the magnetic fields adjacent to each of the electron beams and within the tube neck 24. The coils 42 and the deflection circuits are arranged in conventional fashion to effect con vergence of the electron beams at the plane of the picture reproduction screen as nearly as possible on all points of the screen, regardless of the curvature thereof.

As explained herein it is not possible to position the electron guns with suflicient accuracy to provide convergence of the beam at a single point and Within the plane of the picture reproducing screen. Therefore,

static adjustment of beam convergence may be provided by means of permanent magnets 49 which may be in the form of discs having diametrically opposite magnetic poles. .Each of the discs 49 may be mounted on and 'fixed to a mounting disc 48, in turn attached to a rod 50 rotatively mounted in the end member 51 of section 10, for example, and having a control knob 52 fixed to its outer end by means of a set screw 53. Thus, the permanent magnet 49 may be rotated with respect to pole pieces 45 and 46 to change the relative positions of the magnetic poles and therewith the amount of flux flowing through pole pieces 45 and 46. This alters the static magnetic fields adjacent the two ends of pole pieces 45 and 46 and thereby changes the direction of the cathode ray beam and the point of convergence between the several beams. V

In order to hold the magnet 49 in engagement with pole pieces 45 and 46 and in turn hold pole pieces 45 and 46 in engagement with tube neck 24, the spring 54 is compressed between the end member 51 and a clasp 55 having arms 56 which embrace the magnet 49 and the ends ofpole pieces 45 and 46. In addition to holding pole pieces 45, 46 in engagement with tube neck 24, spring 54 exerts suflicient pressure on the magnet 49 to hold it in whatever adjusted position may be necessary to obtain proper convergence of the electron beams.

.Thus, even though there is a slight amount of wear between pole pieces 45 and 46 and magnet 49 during rotational adjustment thereof, magnet 49 will always hold its adjustment. Such wear can occur in pole pieces and magnets formed of powdered iron.

In order to mount the convergence unit on the tube neck 24 the pin 27 may be disengaged from slot 26 by moving the several frames to the dotted line position indicated by dotted lines 33, 34 and 35. The frame sections 10, 11 and 12 may then be opened by rotating sections 11 and 12 on pins 17 and 19. Then the convergence unit may be moved onto the tube neck 24 and closed to the dotted line position shown by lines 33, 34 and 35. The convergence unit is dimensioned and the pole pieces 45 and 46 are of such length that they engage the neck 24 and move inwardly of the coils 42, compressing the springs 54. Thus, the springs 54 exert pressure suflicient to cause firm engagement of pole pieces 45 and 46 with the outer surface of tube neck 24. When the frame sections are moved to the full line position shown in Fig. 1, pin 27 tends to enter slot 26 and is locked in closed position.

From the foregoing description it will be apparent that this invention provides an electron beam convergence unit which may be easily and quickly mounted on the neck of a picture reproducing tube. The electromagnets are readily and accurately adjustable to provide static and dynamic adjustment of the electron beams and such adjustment is permanent due to the pressure engagement of the magnets with the neck of the picture tube. V

The invention claimed is:

1. A magnet assembly for adjusting beam convergence in a multibeam picture receiving tube, comprising a frame having three sections symmetrically disposed about a common center, two of said sections including hinge structure for pivotally mounting them with respect to the third section, said two sections also including latching means for holding said sections in position about said common center, electromagnets supported within each frame section, each electromagnet comprising a stationary coil, a pair of pole pieces movably supported within said coil and projecting outwardly thereof, a permanent magnet in the from of a disc bridging two adjacent ends of said pole pieces, spring means disposed between a portion of the frame section and said permanent magnet for constantly engaging said permanent magnet with the adjacent ends of said pole pieces and for pressing said pole pieces into engagement with the neck of a picture receiving tube, and a rod attached to said permanent magnet for rotating it with respect to said pole pieces.

2. A magnet assembly for adjusting beam convergence in a multibeam picture receiving tube, comprising a frame having a section for each beam symmetrically disposed about a common center, several of said sections including hinge structure for'pivotally mounting them with respect to another section, latching means for holding said sections in position about said common center, electromagnets supported within each frame section, each electromagnet comprising a stationary coil, a pair of pole pieces movably supported within said coil and pro jecting outwardly thereof, a permanent magnet bridging two adjacent ends of said pole pieces, spring means disposed between a portion of the frame section and said permanent magnet for constantly engaging said permanent magnet with the adjacent ends of said pole pieces and for pressing said pole pieces into engagement with the neck of a picture receiving tube, and means attached to said permanent magnet for rotating it with respect to said pole pieces.

3. A magnet assembly for adjusting beam convergence in a multibeam picture receiving tube, comprising a frame having a section for each beam symmetrically disposed about a comm-on center, electromagnets supported within each frame section, each electromagnet comprising a stationary coil, a pair of pole pieces movably supported within said coil, a permanent magnet bridging two adjacent ends of said pole pieces, spring means disposed between a portion of the frame section and said permanent magnet for constantly engaging said permanent magnet with the adjacent ends of said pole pieces and for pressing said pole pieces into engagement with the neck of a picture receiving tube, and means attached to said permanent magnet for rotating it with respect to said pole pieces.

4. A magnet assembly for adjusting beam convergence in a. multibeam picture receiving tube, comprising a frame having a section for each beam symmetrically disposed about a common center, electromagnets supported within each frame section, each electromagnet comprising a stationary coil, a pair of pole pieces movably supported within said coil, a permanent magnet bridging two adjaeent ends of said pole pieces, and a rod attached to said permanent magnet for rotating it with respect to said pole pieces.

5. A magnet assembly for adjusting beam convergence in a multibeam picture receiving tube, comprising a frame having a section for each beam symmetrically disposed about a common center, magnets supported within each frame section, each magnet comprising a pair of pole pieces movably supported on a frame section radially of said center, a permanent magnet bridging two adjacent ends of said pole pieces, and a rod attached to said permanent magnet for rotating it with respect to said pole pieces.

6. A magnet assembly for adjusting beam convergence in a multi-beam, picture receiving tube comprising a frame having a plurality of sections hinged to one another symmetrically about a common center and corresponding in number to the number of beams in said tube, and electromagnets supported within each frame section and including pole pieces projecting inwardly toward the center of said frame, each electromagnet having an adjustable permanent magnet rotatably mounted on and spring pressed into engagement with the electromagnet for adjustment with respect thereto.

7. A magnet assembly for adjusting beam convergence in a multibeam picture receiving tube, comprising a plural section hinged frame structure, the sections of said frame being symmetrically disposed about a common center, an electromagnet mounted on each section of said frame for generating a magnetic field adjacent said common center, and latch means operatively associated with two adjacent 5 sections of said frame for closing said frame structure with said electromagnets in firm engagement with the neck portion of said tube.

8. A frame for supporting beam Convergence magnets adjacent to a multibeam picture receiving tube, comprising three sections symmetrically disposed about a common center, each section being substantially rectangular, one of said sections including on one corner thereof a first ear having an aperture and on the other corner thereof a flanged extension having a first hinge pin and a stop tab, the second of said sections including on one corner thereof an ear having an aperture for receiving said first hinge pin and the third of said sections including on one corner thereof a flanged extension having a hinge pin mounted within the aperture of said first ear, said third section including on the opposite corner thereof a slotted ear, and said second section including on the opposite corner thereof -a flanged portion including a latch pin receivable in the slot of said slotted ear and a locking tab overlapping said slotted ear portion for holding it in latched relation with respect to said locking pin.

9. A frame for supporting beam convergence magnets adjacent to a multibeam picture receiving tube, comprising three sections symmetrically disposed about a common center, one of said sections including on one corner thereof a first ear having an aperture and on the other corner thereof a flanged extension having a first hinge pin and a stop tab, the second of said sections including on one corner thereof an ear having an aperture for receiving said first hinge pin and the third of said sections including on one corner thereof a flanged extension having a hinge pin mounted Within the aperture of said first ear, said second section and said third section including cooperating latch means for holding said section symmetrically about said common section.

References Cited in the file of this patent UNITED STATES PATENTS 2,157,182 Malofl May 9, 1939 2,541,446 Trott Feb. 13, 1951 2,565,331 Torsch Aug. 21, 1951 2,591,159 Kabuss Apr. 1, 1952 2,743,389 Giutfrida Apr. 24, 1956 

